Electromagnetic reproducer



Sept. 25, 1934.

H. ,1. ROUND ELECTROMAGNETIC REPRODUGER Filed April 1, 1926 INVENTOR HENRY J. ROUND TORNEY Patented Sept. 25 1934 UiTE STATES PA FFIE Henry Joseph Round, London, England, assignor to Radio Corporation of America, a corporation of Delaware Application April 1, 1926, Serial No. 98,961 In Great Britain April 4, 1925 4 Claims.

This invention relates to improvements in electro-magnetic micro-phones or reproducers or recorders of the kind adapted to be actuated by or to cut a phonograph or like record.

In electromagnetic microphones constructed according to the present invention, a stylus or stylus carrier is carried by the magnet and forms a movable or flexible pole piece. Preferably the magnet is provided with adjustable pole tips, and means are provided for damping the vibrations of the stylus or carrier.

In one form of construction I employ a three limb permanent magnet of double U shape, the outer limbs of which are of the same polarity,

15' while the inner limb is of the opposite polarity.

The central limb of the magnet is shorter than the outer limbs and is split or slotted to receive a tongue forming a stylus carrier, located in close proximity to the pole tips of the outer limbs.

The pole tips are movable towards or away from the carrier, and carry coils.

Preferably the outer limbs extend beyond the pole tips and are bored to receive adjustable rods carrying bufiers of resilient material, such as rubber, adapted to damp the vibrations of the carrier or stylus.

The whole is mounted on a fitting adapted to fit the tone arm of an ordinary phonograph, terminals for the coils being carried on an ebonite plate.

In operation, the coils are connected to a loud speaker, preferably through an amplifier.

Obviously an electro-magnetic microphone as above described, is reversible in operation. That is to say, instead of being actuated by a phonograph record to give fluctuating electric currents it may be supplied with fluctuating electric current and employed to cut a phonograph or like record. When used for such a purpose, the stylus is preferably replaced by cutting jewel or the like.

The invention is illustrated in the accompanying drawing, in which Fig. 1 is an elevation of one embodiment of '45; the invention,

Fig. 2 is a reverse elevation and Fig. 3 is an edge view of the same.

Referring to the drawing, 1 is a three limb permanent magnet, the outer limbs of which are of the same polarity, while the inner limb is of oppo- '55: movable away from or towards the carrier by (C1. 1791ll0.41)

means of the screws 5 whereby the total amount of flux and the flux density in the air gap between each pole 4 and carrier 2 may be controlled. The operating coils 6 are carried upon the pole tips 4. The outer limbs of the magnet 1 are extended beyond the pole tips and are bored to receive rods 7 These rods are adjustable and may be held in any position by means of set screws 8 and carry at their ends rubber buffers which contact with the carrier or stylus and thereby serve to damp the vibrations thereof. A fitting 9 adapted to fit the tone arm of an ordinary phonograph is fastened to the microphone to support the same while 10 is a terminal board secured to the front face of the magnet structure by the screws shown and carrying terminals 11 to which the ends of the coil are connected.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed I declare that what I claim is:

l. A phonograph reproducer consisting of a single magnet having two outer limbs of like polarity and an inner limb of opposite polarity extending between said outer limbs, said inner limb being provided with an elongated narrow slot, pole pieces mounted on said outer limbs, an armature having an elongated extension seated in said slot and supported for movement so that one end is always adjacent the inner limb and the other end is adapted to vibrate between said pole pieces, and an operating coil adapted to have electric currents generated therein upon vibration of said armature.

2. A phonograph reproducer comprising an E shaped magnet, the outer limbs of the E shaped magnet being of like polarity and extending beyond the inner limb which is of opposite polarity, said inner limb being provided with a narrow slot, pole pieces on the outer limbs of said magnet, an armature having one end with its opposite faces in close contact with the side walls of said slot and in such a manner that its free end is adapted to vibrate, said like armature extending between said pole pieces, an operating coil positioned to have electric currents generated therein upon vibration of said armature, and means for vibrating said armature associated with its free end.

3. An electromagnetic device comprising an E-shaped permanent magnet having two outer limbs of like polarity, a middle limb of opposite and single polarity, a pole piece mounted on each of said outer limbs and arranged to form a narrow air gap therebetween, a coil mounted on at least one of said pole pieces, a terminal board secured directlysto one face of said magnet terminals omounted on said board and to which said coil is in each pole piece for adjusting the spacing be tween the adjacent ends of said pole pieces a flexible armature having a narrow end portion seated in a recess in said inner limb and extending between said pole pieces, operating coils mounted on said pole pieces, a rod passing through an aperture near the end ofeach outer limb, a bufier of resilient material carried by each rod and in contact with said armature, and means for securing said rods in their adjusted positions HENRY ITOSEPH ROUND. 

